The present invention broadly relates to the field of mobile telecommunications, and specifically to xe2x80x9cflood pagingxe2x80x9d where multiple mobile switching centers (MSCs) are paged to locate a mobile unit that is not where it was last known to be, i.e. not where its last seen pointer (LSP) indicates.
Telephones have become a staple of modem life. Originally telephones were located in peoples"" homes, businesses and in external phone booths. Thanks to changes in the field of telecommunications, people are now able to take advantage of cellular technology, such that mobile units can now be carried along with the users, wherever they may go.
Cellular service providers generally maintain certain information regarding the mobile units to facilitate the proper routing of incoming phone calls to the desired recipients. Further information that needs to be transmitted to the mobile units may include the feature sets, which would dictate the features that are available on the subscribed mobile units. A home location register is able to determine which mobile switching center a subscribed mobile unit last registered with or visited, by referring to a last seen pointer. The home location register is then able to provide the feature set to the mobile unit, transfer incoming calls, for the mobile unit, and transfer outgoing calls from the mobile unit.
As mobile units are by definition mobile, it is very important for the cellular service providers to keep track of their locations. If a mobile unit cannot be located by the cellular service provider, i.e. it is not in the location indicated by the last seen pointer, then the mobile telephone will be non-functional as related to its intended purpose of receiving telephone calls, regardless of its location.
Within a large metropolitan area, several mobile companies will be competing for cellular customers. Consider an area where there are three such companies, A, B, and C. Each such provider will have its own mobile switching centers (MSCs). Further, each company maintains at least one home location register (HLR) for its cellular subscribers. When a call is placed, it may or may not be directed to a customer of the same service provider. The call may originate in many ways. For example, the call may come from outside the area from a distant company, or the caller may be using a non-cellular phone, or it may be from one customer of service provider A to another such customer of service provider A. Or, it may be from a customer of service provider A to a customer of service provider B. Whatever the circumstances, the service provider of the caller must attempt to complete the call to the called mobile unit, regardless of whether the service provider of that called party is service provider A, B, or C.
To facilitate the completion of calls to cellular customers, each provider maintains its own HLRs. When a call is made by a customer of A to a customer of A, then service provider A consults its own HLR to see where the called mobile unit was last located and attempts to complete the call there. But if the call is made by a customer of A to a customer of B, then provider A will request call delivery information from B, and B consults its own HLR to see where the called mobile unit is located and returns information to A regarding how to complete the call. Thus, multiple HLRs may be consulted, depending on the circumstances.
Sometimes the called party (the mobile unit) is not, in fact, located in the same region served by the pointer on the corresponding HLR. Alternatively, the mobile unit may be switched off and not able to receive an incoming call. Whatever the circumstance, the customer""s service provider occasionally will not find the mobile unit at its last known location and will need to find the called unit by a process called flood paging.
Locating a missing mobile unit is therefore an extremely important task in the realm of cellular telecommunications. Sometimes messages will be lost within a telecommunications system and must be delivered to a missing mobile unit. Also, a situation might arise where a mobile unit is moving along a border representing the extreme points where service is provided by a MSC. Depending on where the mobile unit is located as related to the border, multiple MSCs might provide service to a mobile unit, where the mobile unit will be bouncing back and forth between those MSCs. One way of locating a missing mobile unit is through a method called flood paging. Flood paging involves sending location request signals to all of the MSCs under the control of a home location register. The MSC which has control of the mobile unit responds to the location request. When there is only one vendor in the market, such a proprietary method is acceptable.
As the mobile telephone industry is growing very quickly, new parties are entering the cellular telecommunications market. In the future, cellular service providers will invariably have equipment produced by more than one vendor in their telecommunications networks. There is therefore a need for a method in which flood paging can take place across a telecommunications network, regardless of the particular vendor whose equipment is being used.
The current standard for cellular radiotelecommunications intersystem operations provides for one-to-one transactions. For example, when a vendor receives a routing request, it must respond. Further, the standard does not discuss sending out more than one route request per transaction. The current interpretation of the standard does not explicitly state that transactions must be one-to-one. By implementing methods which permissibly deviate from the one-to-one transaction standard, the vendors will be able to allow functions which are currently not available across a multiple vendor system, such as flood paging.
In the preferred embodiment of the present invention, a method for flood paging in a mobile telecommunications system is disclosed, wherein the method comprises the steps of sending a request from a home location register to each of a plurality of mobile switching centers, wherein the request indicates an identifier for a called mobile unit, sending a plurality of pages from the plurality of mobile switching centers, wherein the plurality of pages includes the identifier for the called mobile unit, providing a page response from the called mobile unit to at least one of the plurality of mobile switching centers and providing an acknowledgment of location by at least one of the plurality of mobile switching centers to the home location register.
In another embodiment of the present invention, one or more of the plurality of mobile switching centers does not provide an acknowledgment of location to the home location register.
In an embodiment of the present invention, the home location register forwards a location request signal to a mobile switching center that is attempting to complete the incoming call to the called mobile unit. In a variation of this embodiment, the call is delivered to the first MSC responding with a tldn received by the home location register.
In another embodiment, the home location register maintains an index of the requests sent to each of the plurality of mobile switching centers.
In another embodiment, the home location register makes a determination as to which acknowledgment of location to act upon.
The embodiments further describe in a telecommunications system of the type having a plurality of mobile units, a plurality of mobile switching centers, a called mobile unit and a home location register, the improvement wherein the home location register provides a location request. wherein the plurality of mobile switching centers provide at least one paging signal to the called mobile unit, wherein at least one of the plurality of mobile switching centers is a serving mobile switching center, and wherein only the serving mobile switching center provides a message to the home location register in response to a response to the paging signal.